This invention relates to a drawn cup roller bearing used, for example, as a bearing for a vehicle starter and also to method of producing such a drawn cup roller bearing.
In a conventional drawn cup roller bearing, first, only one end portion of an outer ring is bent (pre-bent) at an angle of 90 degrees to form a rib, and in this condition a cage holding a plurality of rollers and an annular seal with a metal core are mounted in the outer ring, and thereafter the other end portion of the outer ring is bent (post bent) to form a rib, thereby preventing the cage and the annular seal with the metal core from being withdrawn from the outer ring (see, for example, JP-A-2001-99145).
In such a conventional drawn cup roller bearing, first, only the one end portion of the outer ring is bent (pre-bent) to form the rib, and in this condition the cage holding the rollers and the annular seal with the metal core are mounted in the outer ring, and thereafter the other end portion of the outer ring is bent (post bent) to form the rib. Therefore, in order to prevent the development of a crack during the bending operation, only the portion of the heat treated outer ring which is to be post bent is again subjected to induction annealing, or an anti-carbonization treatment is applied only to the portion to be post bent, and by doing so, the hardness is lowered. However, there has been encountered a problem that such method requires an additional step which increase the cost.
Furthermore, when these treatments are applied to the portion of the outer ring to be post bent, there is a possibility that secondary problems, such as a shortened life due to lowered hardness of a raceway and the cracking of the bent portion due to insufficient annealing, arise, and also there has been encountered a problem that a press-fitting direction is limited because of an insufficient strength of the post bent portion.
Furthermore, a sliding contact surface formed at an end portion of the cage contacts the seal, and therefore the annular seal is required to have the metal core so as to prevent damage of the seal due to this contact, which has invited a problem that the cost increases accordingly.
Furthermore, the annular seal is pushed to the end portion of the outer ring. However, there is not provided any means for holding the thus mounted annular seal in position in the axial direction, and therefore in the worse case, there has been encountered a problem that the annular seal is caught by the cage.
Furthermore, in the case where each roller has a large diameter, the size of the annular seal in the radial direction is also increased, which has invited a problem that the material cost of the annular seal increases.